As used herein, the term "vehicle" refers to land vehicles, to marine vehicles or vessels, and to aircraft. In the United States, about 1.7 million automotive vehicles and about 100,000 marine and aircraft vehicles are reported missing (or stolen) each year. The probability that a land or marine vehicle will be recovered drops dramatically after the vehicle or vessel has been missing for 24 hours or more. Thus, time is of the essence in locating and retrieving a missing vehicle.
Sheffer, in U.S. Pat. No. 4,891,650, discloses a vehicle location system that disperses an array of cellular monitoring stations, each of which detects a cellular alarm signal that is transmitted from a vehicle when the vehicle is determined to be missing. Vehicle location is determined at a base station by the relative alarm strength measured at each detector.
U.S. Pat. No. 5,043,736, issued to Damell et al, discloses a portable vehicle locating system that uses a Global Positioning System (GPS) to determine vehicle location, a cellular phone to report this location to a base station, and an interface to convert GPS signals to cellular phone signals for transmission.
A position-aided subscriber unit for a satellite-based cellular phone system is disclosed by Durboraw in U.S. Pat. No. 5,119,341. A GPS unit determines the location of a transceiver on the ground and transmits This location information to a satellite, to increase the efficiency of satellite-to-receiver communication. This apparatus has use in asset management and in search-and-rescue operations.
Wortham, in U.S. Pat. Nos. 5,155,689 and 5,398,190, discloses installation of a mobile cellular phone unit, with its own identification number, an unspecified location determination unit, and an interface between these two units within a vehicle, to determine and transmit vehicle location. This vehicle location information is displayed on a screen in the vehicle and is periodically transmitted to a base station that is located elsewhere.
An airplane theft detection system that includes a dedicated transponder is disclosed by Robinson et al in U.S. Pat. No. 5,159,344. When the aircraft carrying this transponder is stolen, turning on the aircraft engine activates this transponder and deactivates the normal transponder carried by the aircraft. The dedicated transponder then broadcasts a signal to all nearby air controllers that this aircraft has been stolen. This dedicated transponder has its own current leads to a battery and cannot be de-activated by turning off the normal aircraft operations system. A separate, concealed switch allows the dedicated transponder to be deactivated and allows a normal transponder to be activated. This patent discloses no system for determining the present location of the aircraft or for communicating this present location information to a central station.
In U.S. Pat. No. 5,187,805, Bertiger et al disclose a telemetry, tracking and control (TT&C) system for satellite-aided cellular communications. Here, the cells for the cellular phone system move with the satellite used for the link. GPS-determined location of a mobile user station is used to facilitate handoff from one satellite to another as a satellite cell pattern sweeps across a region containing one or several users.
Song discloses a vehicle locating and navigating system in U.S. Pat. No. 5,208,756. A small receiver, hidden on the vehicle, is activated by a plurality of DTMF signals transmitted from telephone stations with fixed, known locations. The vehicle receiver determines the present location of the vehicle, using relative or absolute signal strengths of the received signals and triangulation of these signals. The vehicle location information is then transmitted to a base station, using a voice synthesis and/or digital signals.
A vehicle tracking system that uses an array of spaced apart cellular phone receivers is disclosed in U.S. Pat. No. 5,218,367, issued to Sheffer et al. One or more sensors, such as vehicle break-in sensors, is positioned on a vehicle, and a cellular phone transmitter on the vehicle transmits a cellular signal when a corresponding sensor is activated. The vehicle's location is determined at a base station, using relative signal strengths of these signals, as received at several spaced apart receivers.
U.S. Pat. No. 5,223,844, issued to Mansell, discloses a vehicle tracking and security system that provides vehicle location information where vehicle break-in, theft, breakdown or other unusual events or emergencies occur. Several "mobile units," each including some type of event sensor, are hidden on the vehicle. When a sensor senses occurrence of an alarm condition or event, a mobile unit causes an on-board transmitter to transmit an event alarm or signal to a control center, together with the location of the vehicle as determined by an on-board GPS receiver. The control center then takes appropriate action, depending on the condition or event and the location of the vehicle.
Dennison discloses a cellular phone system that uses GPS-determined location of a vehicle in which the phone unit is carried to make call management decisions, such as call handoff, in U.S. Pat. No. 5,235,633. The vehicle location information is transmitted to a call management site that determines when cell handoff will occur for a given mobile cellular phone unit.
A vehicle occupant personal security system using Loran-based or GPS-based location determination is disclosed by Simms et al in U.S. Pat. No. 5,334,974. When an emergency condition sensor installed on the vehicle senses the presence of an alarm condition, an on-board system activates a cellular phone system and determines the vehicle location. The on-board system then transmits an emergency condition identifier, a vehicle identifier and vehicle location information to a central station, requesting an appropriate response.
What is needed is a system including cellular telecommunication means that allows determination and reporting of the present location of a missing vehicle, using clandestine means on the vehicle itself. Preferably, the cellular means (1) will function in a normal manner, if used by a vehicle occupant while the vehicle is missing, and (2) can be used to determine and transmit a report on the present location of the missing vehicle, if commanded to do so by a central station that communicates with the vehicle. Preferably, the system should allow recording of any telecommunications made using the cellular means while the vehicle is missing.